Field of the Invention
In public energy networks, for example energy distribution and energy transmission networks, the maintenance of the voltage quality is coming to the fore more and more on account of the greatly heterogeneous load and producer structure caused by decentralized energy producers. It is necessary to comply with the standard EN 50160, for example, which requires a voltage band of +/−10% of the nominal voltage of the energy network for all network operating situations. This is becoming more and more difficult with the conventional control methods (static control in the local network stations (ONS) and the substations). Therefore, controllable local network transformers (RONT) or network controllers are increasingly being used. One example of this problem and accordingly used controllable local network transformers and network controllers is found in the lecture “Pilotprojekte zur Spannungsregelung im NS-Netz der Thüringer Energie”, VDE symposium, Meissen Sep. 18, 2013, by DipI.-Ing. Torsten Roscher, Thüringer Energie AG in Erfurt.
The products and their installation sites are selected on the basis of field tests or operational empirical values. Coordination with the control devices which are still present in the network must be dispensed with on account of the complexity or is carried out only in a rudimentary manner by means of tests. Therefore, such a procedure is not optimal either operationally or economically. In order to arrive at a result which is optimal both under the aspect of energy losses and under the aspect of investment costs when planning an energy network, all control devices (desired value in the substation, construction or non-construction of medium-voltage network controllers, adjustment of the tap changers in the conventional local network stations, replacement of selected local network station transformers with controllable local network transformers, installation of network controllers in the low voltage) would have to be taken into account for all relevant operating situations.
Controllable local network transformers are offered by numerous manufacturers, the different devices differing in terms of their possibilities for controlling the voltage, the procurement and maintenance costs and the design-related energy losses. Controllable local network transformers are generally priced between 22,000 and 25,000 and therefore are currently approximately twice as expensive as conventional local network transformers. Therefore, the use and installation site of a controllable local network transformer should be accurately planned. In this case, the so-called cash value denotes the procurement costs plus cumulative operating costs over the planned operating duration of an item of equipment, for instance a transformer.
With regard to the operation-related energy loss of the various device types, test measurements must generally be carried out in various operating situations. In this case, an increased energy loss on account of a more complicated design must often be accepted in the case of a high degree of flexibility, for example if many different control stages are provided on a transformer.
For example, the information brochure “Die intelligente Ortsnetzstation—Ein wichtiger Smart Grid-Baustein”, SEEDEFOSMARKTKIOSK_12-12_1.1 from 2012 from Schneider Electric Energy GmbH discloses, on page 7, a local network transformer which can be electronically controlled in an infinitely variable manner.
The product information “FITformer® REG—Der regelbare Ortsnetztransformator”, order no. E50001-G640-A220-V2, TH 101-140819 DB 10140.3 from 2014 discloses a three-stage transformer.
Network controllers are known, for example, from the product information “Netzregler” from Walcher GmbH & Co. KG. The product information “Magtech-Netzregler: Spezialist für Netzausläufer mit Photovoltaik-Anlagen” also discloses a network controller.
International patent disclosure WO 2012/037989 A1 discloses a method for the computer-assisted distribution of energy in a decentralized energy network, in which improved control of active powers provided at various points of the energy network by a mathematical optimization method during operation of the energy network is proposed. In this case, in particular, the energy consumption and the energy supply of decentralized energy consumers and energy producers, respectively, are controlled by evaluating measured values.
Furthermore, international patent disclosure WO 2010/0357516 A1 discloses a method for determining electrical load flows in an electrical energy supply network, load profiles of consumers being dynamically adapted during operation of the energy supply network using measured values.
In this case, it has hitherto been conventional to investigate only partial aspects with regard to the planning of an energy network during planning on account of the complexity of a typical energy network and its controllable devices. For this purpose, possible locations of controllable local network transformers are predefined as part of a few variants devised by a planner and are evaluated with the aid of load flow simulations. On account of the large number of possible solutions, partial aspects or correlations between the aspects must be entirely disregarded in this procedure in order to achieve a result in a finite time.
Alternatively, lengthy field tests or measurements for assisting with the finding of a solution have also been carried out for a long time.
On the basis of known approaches for planning an electrical energy network having controllable devices for transmitting energy, the invention is based on the technical object of specifying a method for retrofitting the energy network, which method enables a high voltage quality even with increased decentralized energy supply with comparatively little retrofitting effort and/or low energy losses.